Automatic image convergence for projection television systems

Abstract

Systems and methods that facilitate automatic convergence and geometry alignment in projection systems such as a PTV. The automatic convergence system (ACS) preferably includes a CCD camera mounted inside the PTV and focused on the entire inside of a projection screen Fresnel lens. Alternatively, the ACS may include a deployable reflective sheet, preferably in the form of a roll up screen. In operation, signals from the CCD camera corresponding to test patterns projected onto the Fresnel lens or reflective sheet are analyzed and used to align, center or steer raster patterns to compensate for convergence error at a particular location. In a convergence mode, the video is blanked and then successive monochrome video test patterns are projected on the screen. The images captured by the CCD camera are used to memorize the location of landing points of one color test pattern from one of the projection units and then to align the other color patterns from the other projection units to the same landing points as the first color pattern. In a geometry alignment mode, the difference in brightness between an image striking the Fresnel screen and the over scanned area of the PTV cabinet is used to determine the border of the screen. This information is then used to provide reference marks for all geometrical adjustments done automatically using a similar process of successive test patterns and analysis.

1. A method for automatic geometric alignment in a CRT projection system comprising the steps of
 displaying a first image pattern onto a screen of the CRT projection system, wherein the screen includes a Fresnel lens, 
 reflecting back a portion of the light from the first image off of the Fresnel lens, 
 identifying the boundaries of the screen, 
 calculating optimum locations based on screen boundary coordinates, 
 displaying a second image pattern, 
 moving the second pattern to a first optimum location, 
 reporting the actual location of the second image pattern, 
 comparing the actual location of the second image pattern with the coordinates of the first optimum location, and 
 aligning the second image pattern with the first optimum location. 
 
     
     
       2. The method of  claim 1  wherein the first image pattern comprises a flat green field projected onto the screen and onto an over scanned area. 
     
     
       3. The method of  claim 2  wherein the step of identifying the boundaries of the screen includes analyzing the difference in brightness of the reflected images reflected off of the screen and the over scanned area. 
     
     
       4. The method of  claim 1  wherein aligning the second image pattern with the first calculated optimum location includes adjusting the size or centering of the second image pattern. 
     
     
       5. The method of  claim 1  further comprising the steps of
 moving the second pattern to a second optimum location, 
 reporting the actual location of the second image pattern, 
 comparing the actual location of the second image pattern with the coordinates of the second optimum location, and 
 adjusting the position of the second image pattern to align the second image pattern with the first calculated optimum location. 
 
     
     
       6. The method of  claim 1  wherein the step of calculating optimum locations based on screen boundary coordinates includes calculating n optimum locations and further comprising the steps of
 moving the second pattern to n optimum locations, 
 reporting the actual location of the second image pattern at each of the n optimum locations, 
 comparing the actual location of the second image pattern at each of the n optimum locations with the coordinates of each of the n optimum locations, and 
 aligning the second image pattern at each of the n optimum locations with the each of the n optimum locations. 
 
     
     
       7. A method for automatic convergence alignment in a CRT projection system comprising the steps of
 displaying a first image pattern a first location on a screen comprising a Fresnel lens, 
 reflecting back a portion of the light from the first image off of the Fresnel lens, 
 identifying and storing the coordinates of the first location of the first image pattern, 
 moving the first image pattern to a second location, 
 identifying and storing the coordinates of the second location of the first image pattern, 
 displaying a second image pattern, 
 adjusting the second image pattern to move the second image pattern to the top center of the first location of the first image pattern, 
 reporting the actual location of the second image pattern, 
 comparing the actual location of the second image pattern with the coordinates of the first location of the first image pattern, and 
 aligning the second image pattern with the first location of the first image pattern. 
 
     
     
       8. The method of  claim 7  further comprising steps of
 moving the second image pattern to a second location, 
 adjusting the second image pattern to move the second image pattern to the top center of the second location of the first image pattern, 
 reporting the actual location of the second image pattern, 
 comparing the actual location of the second image pattern with the coordinates of the second location of the first image pattern, and 
 aligning the second image pattern with the second location of the first image pattern. 
 
     
     
       9. The method of  claim 8  further comprising the steps of
 displaying a third image pattern, 
 adjusting the third image pattern to move the third image pattern to the top center of the first location of the first image pattern, 
 reporting the actual location of the third image pattern, 
 comparing the actual location of the third image pattern with the coordinates of the first location of the first image pattern, and 
 aligning the third image pattern with the first location of the first image pattern. 
 
     
     
       10. The method of  claim 9  further comprising steps of
 moving the third image pattern to a second location, 
 adjusting the third image pattern to move the third image pattern to the top center of the second location of the first image pattern, 
 reporting the actual location of the third image pattern, 
 comparing the actual location of the third image pattern with the coordinates of the second location of the first image pattern, and 
 aligning the third image pattern with the second location of the first image pattern. 
 
     
     
       11. The method of  claim 10  wherein the first, second and third image patterns comprise a movable monochromatic geometric shape. 
     
     
       12. The method of  claim 8  further comprising the steps of
 moving the first image pattern to n locations, 
 identifying and storing the coordinates of the first image pattern at each of the n locations, 
 moving the second image pattern to each of the n locations, 
 adjusting the second image pattern to move the second image pattern to the top center of each of the n locations of the first image pattern, 
 reporting the actual location of the second image pattern at each of the n locations, 
 comparing the actual location of the second image pattern at each of the n locations with the coordinates of the first image pattern at each of the n locations, and 
 aligning the second image pattern at each of the n locations with each of the n locations of the first image pattern.